JP3486838B2 - High-temperature heating element, high-temperature electrode material, luminescent material, and high-temperature thermocouple material made of high melting point conductive oxide - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an electrically conductive material having the highest melting point in an atmosphere containing oxygen. Further, the present invention relates to a heating element that utilizes heat generated by energization in an atmosphere containing oxygen, an electrode material that can be used at high temperatures, a high temperature light emitting material such as a filament material for a lamp, a high temperature thermocouple material, and the like.

[0002]

2. Description of the Related Art In an electric furnace utilizing resistance heating, a heating element material to be used is selected according to its application. In air or in an oxygen atmosphere, a silicon carbide SiC heating element (trade name: Siliconit R) can be used at a maximum of about 1600 ° C., and a molybdenum silicon MoSi ₂ heating element (trade name: Kanthal Super R) can be used at a maximum of about 1700 ° C. Also, the melting point of platinum (Pt) and platinum-rhodium (Pt-Rh) metal wires is 1769 ° C.
Therefore, it can be used up to about 1500 ° C.
Each electric resistivity is almost metallic, including temperature dependence. A lanthanum chromite heating element (trade name KERAMAX R), which is an oxide of lanthanum and chromium, has a semiconducting temperature dependence, but its electrical resistance is relatively small.
There are general-purpose electric furnaces capable of obtaining temperatures up to about 900 ° C. To obtain a higher temperature by the resistance heating method,
Zirconia with a melting point or decomposition temperature of 2000 ° C or higher (Z
rO ₂ ) and thoria (ThO ₂ ) will be used.
Since these oxides are semiconductors, current cannot flow unless the temperature is set to 1000 ° C. or higher. That is, since it is necessary to use it together with another heating element, a general-purpose electric furnace using these oxides as a heating element has not been realized. In a reducing atmosphere such as hydrogen or a rare gas, refractory metals such as molybdenum (Mo), tantalum (Ta), and tungsten (W) are 2000 ° C., 2100 ° C., and 25 ° C., respectively.
Used to obtain high temperatures up to 00 ° C. These heating elements have very little oxygen (10 ⁻⁵ Torr).
In the above), an oxide is easily formed and the electric resistance of the heating element is increased, so that it cannot be used in an oxygen atmosphere.

Ruthenium (Ru) and iridium (I
Noble metals such as r) and rhodium (Rh) are themselves high melting point metals (ruthenium: 2250 ° C., iridium:
2457 ° C, rhodium: 1963 ° C). However, these metals easily evaporate or oxidize at high temperatures in an oxidizing atmosphere. Further, since it is a noble metal, its price is very expensive (several times or more that of gold), and it is extremely difficult to use it as a realistic heating element material because it is not easily processed. In the present invention, an oxide containing Sr and Ru that does not change in material due to such temperature is used as a heating element material in an oxidizing atmosphere. That is, Sr-
The present invention has revealed that Ru oxide is an electrically conductive (metallic) material having the highest melting point in an atmosphere containing oxygen. Ru (ruthenium) is relatively expensive,
Since strontium and oxygen are contained, the price per unit volume is low, and the processing is relatively easy, similar to that of Siliconit R. Also, a patent has been published that uses an oxide of a noble metal such as ruthenium, iridium, or rhodium or an oxide of any of these and other elements in a high-frequency heating element (see Japanese Patent Laid-Open No. 6-223960). The present invention is intended for heating by microwave absorption in an oven microwave oven or the like, and its characteristic is that the temperature rising characteristics are good when the above-mentioned material is used for a heating element for high frequency heating. The assumed temperature range is about 600 ° C to 870 ° C.
This is essentially different from the one intended for a temperature of about 00 ° C.

[0004]

Conventionally, it has been possible to achieve a temperature of 2000 ° C. or higher by resistance heating in hydrogen.
Only when a refractory metal such as tungsten was used as a heating element in a reducing atmosphere such as a rare gas. This is because there was no suitable material having a metallic electric resistance having a melting point of about 2000 ° C. in an oxidizing atmosphere. That is, there was no method for generating a high temperature of 1700 ° C. or higher using resistance heating in an oxidizing atmosphere. 170 in an oxidizing atmosphere for the same reason
There was also no thermocouple material for measuring high temperatures above 0 ° C. However, if there is a material with a metallic electric resistance that has a melting point of about 2000 ° C. in an oxidizing atmosphere, by providing a temperature range that could not be realized by the resistance heating method and using it as an electrode at high temperature, It is possible to measure temperature with a thermocouple.

[0005]

The present invention has been devised in order to meet such a demand, and can easily obtain a high temperature of 1700 ° C. or higher mainly by resistance heating in an oxidizing atmosphere. For use under high temperature of 1700 ℃ or higher in oxidizing atmosphere
The purpose is to obtain an electrode material that has In order to achieve the object, the present invention is characterized by using an oxide containing Sr and Ru as a heating element for resistance heating. As described above, the Sr—Ru oxide is an electrically conductive (metallic) material having the highest melting point (up to 2000 ° C.) in an atmosphere containing oxygen, and is effective in solving the above problems. The oxides containing Sr and Ru include Sr ₂ RuO ₄ and Sr ₃ Ru.
₂ O ₇ , SrRuO _{3 and the} like. These oxides are obtained by mixing raw material strontium carbonate (SrCO ₃ ) and ruthenium dioxide (RuO ₂ ) in the same proportion as the target composition, and sintering the mixture in air at a temperature of 900 ° C to 1300 ° C. You can get it.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the examples of the present invention, strontium and ruthenium are used in the form of carbonate or oxide, but any form of compound may be used. The particle size of the powder is preferably several tens to several hundreds of microns, but if mixed well, the particle size does not matter. Furthermore, the same applies to the particle size distribution. The ultrahigh melting point conductive material of the present invention is basically composed of Sr ₂ RuO ₄ , Sr.
₃ Ru ₂ O ₇ , SrRuO _{3 and the} like, but it is sufficient if the object can be achieved even if a known heat resistant material is mixed.
Further, although the ultrahigh melting point conductive material of the present invention can be used in an oxidizing atmosphere up to about 2000 ° C., it goes without saying that it can also be used in a weak reducing atmosphere. In the present invention, the light emitting material means a cathode material represented by a filament or an electron emitting material.
The embodiments of the present invention are summarized as follows. (1) A powdered Sr compound and a Ru compound or Ru metal are mixed and sintered at 900 to 1300 ° C. in an oxygen-containing atmosphere, and then the sintered body is crushed again and molded, and then an oxygen-containing atmosphere again. Sr-Ru oxide sintered body or powdered SrCO, which was sintered in an atmosphere containing oxygen and was stable up to 2000 ° C. in an atmosphere containing oxygen, and had a metallic electric conductivity. ₃ and RuO ₂ are mixed and in air 9
After sintering at 00 to 1300 ° C., the sintered body is pulverized again, molded, and then sintered again at 1000 to 1500 ° C. in air, which is stable up to 2000 ° C. in an oxygen-containing atmosphere, and
Second Sr-Ru oxide sintered body showing a metallic electrical conductivity, or the first or second Sr-Ru oxide sintered body was melted by using the focused infrared rays, re A heating element for high temperature, which is made of a crystallized Sr-Ru oxide single crystal and is used in an atmosphere containing oxygen. (2) Powdery Sr compound and Ru compound or Ru metal are mixed and sintered at 900 to 1300 ° C. in an oxygen-containing atmosphere, and then the sintered body is crushed again and molded, and then again oxygen-containing atmosphere. Sr-Ru oxide sintered body or powdered SrCO, which was sintered in an atmosphere containing oxygen and was stable up to 2000 ° C. in an atmosphere containing oxygen, and had a metallic electric conductivity. ₃ and RuO ₂ are mixed and in air 9
After sintering at 00 to 1300 ° C., the sintered body is pulverized again, molded, and then sintered again at 1000 to 1500 ° C. in air, which is stable up to 2000 ° C. in an oxygen-containing atmosphere, and
Second Sr-Ru oxide sintered body showing a metallic electrical conductivity, or the first or second Sr-Ru oxide sintered body was melted by using the focused infrared rays, re A high-temperature electrode material used in an atmosphere containing oxygen, which is composed of a crystallized Sr-Ru oxide single crystal. (3) Powdery Sr compound and Ru compound or Ru metal are mixed and sintered at 900 to 1300 ° C. in an atmosphere containing oxygen, and then the sinter is crushed again and molded, and then an atmosphere containing oxygen again. First Sr-Ru oxide sintered body or powdered SrCO sintered at 1000 to 1500 ° C., stable up to 2000 ° C. in an oxygen-containing atmosphere, and showing metallic electrical conductivity ₃ and RuO ₂ are mixed and in air 9
After sintering at 00 to 1300 ° C., the sintered body is pulverized again, molded, and then sintered again at 1000 to 1500 ° C. in air, which is stable up to 2000 ° C. in an oxygen-containing atmosphere, and
Second Sr-Ru oxide sintered body showing a metallic electrical conductivity, or the first or second Sr-Ru oxide sintered body was melted by using the focused infrared rays, re A phosphor material used in an atmosphere containing oxygen, which is composed of a crystallized Sr-Ru oxide single crystal. (4) Powdery Sr compound and Ru compound or Ru metal are mixed and sintered in an oxygen-containing atmosphere at 900 to 1300 ° C., and then the sinter is crushed again and molded, and then again in an oxygen-containing atmosphere. First Sr-Ru oxide sintered body or powdered SrCO sintered at 1000 to 1500 ° C., stable up to 2000 ° C. in an oxygen-containing atmosphere, and showing metallic electrical conductivity ₃ and RuO ₂ are mixed and in air 9
After sintering at 00 to 1300 ° C., the sintered body is pulverized again, molded, and then sintered again at 1000 to 1500 ° C. in air, which is stable up to 2000 ° C. in an oxygen-containing atmosphere, and
Second Sr-Ru oxide sintered body showing a metallic electrical conductivity, or the first or second Sr-Ru oxide sintered body was melted by using the focused infrared rays, re A material for a high temperature thermocouple used in an atmosphere containing oxygen, which is composed of a crystallized Sr-Ru oxide single crystal.

Example 1 (Production of oxide Sr ₂ RuO ₄ ) SrCO ₃ and RuO ₂ were mixed at a molar ratio of 2: 1 and finely and thoroughly mixed in an agate mortar, followed by sintering in air at 1200 ° C. for 24 hours. did. The sinter was crushed and mixed again, pressed into a rod shape with a diameter of 6 mm and a length of 200 mm, and then molded in air 13
Sr ₂ RuO ₄ sintered rods were prepared by sintering at 00 ° C. for 3 hours.

Example 2 (High-Temperature Electrical Properties of Oxide Sr ₂ RuO ₄ ) The Sr ₂ RuO ₄ sintered rod prepared in Example 1 was placed in an infrared image furnace equipped with a halogen lamp and a spheroidal reflecting mirror in an air atmosphere. I set it in. Electrical resistance measurement terminals were attached to both ends of the sintered rod with silver paste, and the highest temperature portion T ₀ where infrared rays were concentrated was measured with a radiation thermometer. In this state, the lamp voltage was increased while measuring the electrical resistance by the 4-terminal method using a digital multimeter. When the temperature reached about 2100 ° C., the Sr ₂ RuO ₄ sintered rod started to melt. Although the electric resistance increases as the temperature rises, as shown in FIG.
ohm). In FIG. 1, I +,
I- is a current terminal, V +, V- are voltage terminals, the whole sintered rod is not at the same temperature, and the highest temperature portion where infrared rays are concentrated is the center of the sintered rod and the temperature T here. ₀ was measured. The horizontal axis of the graph plots the temperature. The temperature decreases as the distance from the center of the sintered rod increases, so that T ₀ > T ₁ > T ₂ . Therefore, Sr-up to 200 ° C or more (2000 ° C) higher than platinum (melting point 1770 ° C), which has been known to show metallic electric conductivity up to its melting point in an atmosphere containing oxygen.
The Ru oxide was found to exist stably. That is, S
The r-Ru oxide is a metallic electrically conductive material having the highest melting point in an atmosphere containing oxygen. Therefore, it was found that Sr ₂ RuO ₄ can be sufficiently applied as a heating element for resistance heating in an oxidizing atmosphere up to a high temperature of about 2000 ° C. At the same time, it was also found that Sr ₂ RuO ₄ can be applied as a high temperature electrode material in an oxidizing atmosphere, a thermocouple material, or a lamp filament utilizing light emission by energization. Example 3 (Production of oxide Sr ₂ RuO ₄ single crystal) As in Example 2, the Sr ₂ RuO ₄ sintered rod was set in an infrared image furnace equipped with a halogen lamp and a spheroidal reflector in an air atmosphere. , The lower end of the sintered rod suspended from the upper part of the growth space was melted by increasing the lamp voltage, and then fixed to the lower part of the growth space with the same composition of Sr ₂ Ru.
The molten portion is held by bringing it into contact with an O ₄ sintering rod. In this state, the molten portion is slowly moved (20 mm / h) to the upper portion to obtain an Sr ₂ RuO ₄ single crystal.

[0009]

As described above, the Sr-Ru oxide sintered body has the highest melting point among the conductive oxides in the oxidizing atmosphere and has the metallic electric resistance up to that temperature. I knew that. Therefore, in the present invention, Sr-R
The u oxide sintered body can be used as a heating element for generating high temperature by resistance heating at 1700 ° C. or higher in an oxidizing atmosphere, and
It can be used as a high temperature electrode material or a light emitting material in an atmosphere containing oxygen. Similarly, by using the Sr—Ru oxide sintered body as a thermocouple material, a high temperature of 1700 ° C. or higher in an oxidizing atmosphere can be measured.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a relationship between electric resistance and temperature of a Sr ₂ RuO ₄ sintered rod.

[Explanation of symbols]

I +, I- Current terminal V +, V- Voltage terminal T ₀ Temperature of central part of sintered rod T ₁ , T ₂ Temperature of peripheral part of sintered rod

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinichi Ikeda 1-4 Umezono, Tsukuba-shi, Ibaraki Electronics Technology Research Institute (72) Inventor Naoki Shirakawa 1-4-1 Umezono, Tsukuba-shi, Ibaraki Industry (72) Inventor Hiroshi Bando 1-1-4 Umezono, Tsukuba City, Ibaraki Prefectural Institute of Industrial Technology (56) Reference JP 2000-44390 (JP, A) 5-23042 (JP, B2) (58) Fields surveyed (Int.Cl. ⁷ , DB name) C04B 35/00-35/22 C30B 1/00-35/00 H01B 1/00-1/24 H05B 3 / 02-3/18 H05B 3/40-3/82

Claims (4)

(57) [Claims] 1. A powdery Sr compound and Ru compound or R
900 to 130 in an atmosphere containing oxygen by mixing u metal
After sintering at 0 ° C., the sintered body was crushed again, shaped, and then sintered again at 1000 to 1500 ° C. in an oxygen-containing atmosphere, which was stable up to 2000 ° C. in an oxygen-containing atmosphere, and
The first Sr—Ru oxide sintered body showing metallic electric conductivity, or SrCO ₃ and RuO ₂ in powder form were mixed and sintered in air at 900 to 1300 ° C. A second Sr-Ru oxide that is crushed, molded, and then sintered again in air at 1000 to 1500 ° C., that is stable up to 2000 ° C. in an oxygen-containing atmosphere and that exhibits metallic electrical conductivity. A sintered body, or the first or second Sr-Ru oxide sintered body ,
Sr melted and recrystallized using focused infrared rays
-Ru oxide single crystal, containing oxygen and 1700 degrees or more
High temperature heating element used in the above atmosphere. 2. Powdered Sr compound and Ru compound or R
900 to 130 in an atmosphere containing oxygen by mixing u metal
After sintering at 0 ° C., the sintered body was crushed again, shaped, and then sintered again at 1000 to 1500 ° C. in an oxygen-containing atmosphere, which was stable up to 2000 ° C. in an oxygen-containing atmosphere, and
The first Sr—Ru oxide sintered body showing metallic electric conductivity, or SrCO ₃ and RuO ₂ in powder form were mixed and sintered in air at 900 to 1300 ° C. A second Sr-Ru oxide that is crushed, molded, and then sintered again in air at 1000 to 1500 ° C., that is stable up to 2000 ° C. in an oxygen-containing atmosphere and that exhibits metallic electrical conductivity. A sintered body, or the first or second Sr-Ru oxide sintered body ,
Sr melted and recrystallized using focused infrared rays
-Ru oxide single crystal containing oxygen 1700 degrees or more
High temperature electrode material used in the atmosphere. 3. Powdered Sr compound and Ru compound or R
900 to 130 in an atmosphere containing oxygen by mixing u metal
After sintering at 0 ° C., the sintered body was crushed again, shaped, and then sintered again at 1000 to 1500 ° C. in an oxygen-containing atmosphere, which was stable up to 2000 ° C. in an oxygen-containing atmosphere, and
The first Sr—Ru oxide sintered body showing metallic electric conductivity, or SrCO ₃ and RuO ₂ in powder form were mixed and sintered in air at 900 to 1300 ° C. A second Sr-Ru oxide that is crushed, molded, and then sintered again in air at 1000 to 1500 ° C., that is stable up to 2000 ° C. in an oxygen-containing atmosphere and that exhibits metallic electrical conductivity. A sintered body, or the first or second Sr-Ru oxide sintered body ,
Sr melted and recrystallized using focused infrared rays
-Ru oxide single crystal containing oxygen 1700 degrees or more
Luminescent material used in the atmosphere. 4. Powdered Sr compound and Ru compound or R
900 to 130 in an atmosphere containing oxygen by mixing u metal
After sintering at 0 ° C., the sintered body was crushed again, shaped, and then sintered again at 1000 to 1500 ° C. in an oxygen-containing atmosphere, which was stable up to 2000 ° C. in an oxygen-containing atmosphere, and
The first Sr—Ru oxide sintered body showing metallic electric conductivity, or SrCO ₃ and RuO ₂ in powder form were mixed and sintered in air at 900 to 1300 ° C. A second Sr-Ru oxide that is crushed, molded, and then sintered again in air at 1000 to 1500 ° C., that is stable up to 2000 ° C. in an oxygen-containing atmosphere and that exhibits metallic electrical conductivity. A sintered body, or the first or second Sr-Ru oxide sintered body ,
Sr melted and recrystallized using focused infrared rays
-Ru oxide single crystal containing oxygen 1700 degrees or more
Material for high temperature thermocouples used in the atmosphere.